Agilent Technologies 4395A - Page 290

Reection
Measurement
(NA)
Impedance
Measurement
The
amount
of
power
reection
from
a
device
is
directly
related to
the impedance
values of
both
the
device
and
the
measuring
system. In
fact, each
value of
the reection
coecient (0)
uniquely
denes
a
device
impedance
.
For
example:
0=0
occurs
when
the
device
and
test set
impedance are
the same
.
A
short
circuit
has
a
reection
coecient
of
0=1
6
180

(=
0
1).
An
open
circuit
has
a
reection
coecient of
0=1
6
0

(=1).
Every
other
value
for
0
also
corresponds uniquely
to a
complex device
impedance,
according
to
the
equation:
Z
n
=
1
+0
1 0
0
Where
Zn
is
the
DUT
impedance
normalized
to
(that
is
,
divided
by)
the
measuring
system's
characteristic
impedance
(usually
50
or
75
).
The
network
analyzer
has
a
default
impedance
of
50 .
T
o
set
the
impedance
to
75
,
press
4
Cal
5
N
N
NN
NN
N
N
N
N
N
N
N
N
MORE
N
NN
NN
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
SET
Z0 .
The
network
analyzer
uses
the
formula
above
to
convert
the
reection
coecient
measurement
data
to
impedance
data.
1.
Press
4
F
o
rmat
5
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
NN
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
SMITH
CHART
.
The
display
shows
the
complex
impedance
of the
DUT over
the
frequency
range
selected.
2.
Press
4
Ma
rk
er
5
to
turn on
the marker
.
Then
use
the
knob
to
read
the
resistive
and
reactive
components
of
the complex
impedance at
any
point
along
the
trace
.
The
marker
displays
a
complex
impedance
readout.
Figure 10-12. Impedance Measurement
10-12 Examples of Applications